A semiconductor manufacturing process requires a technique to measure the width, height and wall angle of a pattern, and the micro shapes of the top and bottom of a wiring line. As a non-destructive and non-contact inspection apparatus, there has been known an apparatus which uses grazing incidence small angle X-ray scattering (GISAXS) that is reflective CD-SAXS. This apparatus uses the small angle scattering of X-rays to measure a shape, and totally reflects the X-rays on the surface of a substrate. This apparatus is therefore particularly advantageous to surface shape measurement. However, the apparatus has a drawback of being unable to measure an internal stack structure because the X-rays are totally reflected by the substrate surface and do not enter the structure. In the meantime, an X-ray reflectometer (XRR) technique is known as a technique to measure a stack structure. This technique uses interference resulting from the reflection of X-rays in each layer. This technique is generally used to measure an internal stack structure with no pattern structure. If there is a pattern structure, the measurement of the thickness of the internal structure is difficult because of interference conditions that are changed by the pattern structure and because of the effect of surface scattering.